In conduit assemblies and particularly conduits formed from material for use as sewer pipes and the like, the pipes are typically joined end-to-end and provided with a sealing means to seal the joints from the fluid flowing inside the pipe. With nonmetallic pipes, such as concrete, special sealing means are employed to achieve the desired seal at the joint. The seals employed heretofore have been steel ring inserts secured to the ends of the concrete pipe and configured to hold rubber gaskets such that, when the pipes are joined, the gaskets will be compressed to seal the joint. In manufacturing pipes with sealing inserts, the inserts have been included with the concrete pipe forms and in a manner which allows the slurry to flow into the form and harden to hold the insert in place, after the forming process is complete.
An example of these sealing systems include the U.S. Pat. to Bower No. 3,858,912. This Bower patent relates to the use of inserts for nonmetallic pipes where each insert has a groove for receiving an O-ring type sealing member. Each of these inserts has flanges at the ends of the inserts whose primary purpose is to inhibit the accumulation of concrete into these grooves during the forming process. In addition, these flanges serve to anchor the inserts in place. There is also ancillary reference made to the use of these flanges along with the groove as inhibiting leakage between the inserts and the concrete pipe. The U.S. Pat. to Cleverly No. 2,770,476 employs plastic inserts, one in the bell end and another in the spigot end of the pipe, to seal the joints formed when the bell end is telescopically engaged over the spigot end of a complementary pipe. Annular grooves are provided in the bell wall of the pipe allowing the bell insert to be secured in interlocking relationship with the pipe.
The U.S. Pat. to Elder et al, No. 3,764,151, relates to a multibore concrete section of the bell and spigot type pipe formed integrally with preformed end liners or inserts. These inserts are arranged within a mold to be molded in place as the pipe is formed by pouring the slurry into the mold. These inserts are held in place by stages and platens during the molding process.
Other prior art showing joining systems include the following U.S. Pat. Nos. 2,995,322 to Hite, Oct. 11, 1960; 3,201,136 to G.C. Harrison et al., Aug. 17, 1965; 3,503,636 to Bower, Mar. 31, 1970; 3,516,447 to Pittman, Jr., June 23, 1970; 3,592,481 to Jeffery et al, July 13, 1971; and 3,807,744 to Gibling, Apr. 30, 1974.
There are several problems associated with pipe sealing systems which have not been overcome by the prior art cited above. The sealing ends incorporated with the pipes which have characterized the prior art, although achieving some seal, have failed to achieve the smooth surface-to-surface engagement which ensures a good seal in the joints over substantial periods of time. In addition, many of these seals do not effecitvely seal the interface between the end seal and the pipe to which it is attached. As a result, although the joint can be sealed between the two end seals, another path along this interface is available for possible leakage negating the effect of the end seals. This problem has not been effectively overcome by the prior art discussed above. Further, some of the seals disclosed above are not efficient from an economic standpoint. For example, some of the seals call for unusually convoluted configurations which are expensive to mold and difficult to employ properly. Many of the seals which have characterized the prior art are not properly secured to the end portion of the pipe. The result is that they may break away during the joining operation or some time after the joint has been made.